Medical ultrasound has gained increased popularity as a diagnostic tool. A number of techniques for estimating the velocity of biological tissue using ultrasonic energy have been investigated, and some of these techniques are now considered standard clinical practice. For example, Doppler ultrasound techniques have been used to estimate the velocity of blood flow for some time by processing echoes generated by multiple transmissions and receptions of ultrasonic energy formed into a beam that can be steered in the region being investigated to measure frequency or phase shift.
Doppler techniques, however, may produce inaccurate results if the Doppler beam is not steered accurately. Accurately steering the Doppler beam may be difficult, however, when using a conventional two dimensional (2D) ultrasound scan. For example, a conventional 2D ultrasound system may produce a B slice image that represents a slice of the region being imaged. Unfortunately, the operator may experience difficulty in accurately steering the Doppler beam to the desired portion of a region using the conventional B slice which may reduce the accuracy of the estimated velocity of the biological tissue or affect estimates relating to the extent of the condition being examined. For example, if the Doppler beam is not steered to the desired portion of a heart valve being imaged, the determined size of the hole in heart valve may be wrong or the velocity of a jet due to a hole in the heart valve may be inaccurate.
In view of the above, there is a need to allow improved methods and systems for estimating the velocity of tissue using Doppler ultrasound techniques.